Liliana Morales-Barrera

Biosorption of Ni(II) from aqueous solutions by Litchi chinensis seeds.

The potential of Litchi chinensis seeds (LCS) for biosorption of Ni(II) ions from aqueous solutions was investigated in batch systems in terms of kinetics, equilibrium and thermodynamics. Experimental data showed that the biosorption capacity of LCS was dependent on operating variables such as solution pH, initial Ni(II) concentration, contact time, and temperature. The optimum pH value for Ni(II) biosorption was 7.5. Significant enhancement of Ni(II) biosorption was observed by increasing initial metal concentration and temperature. Modeling of sorption kinetics showed good agreement of experimental data with the pseudo-second-order kinetic model. Langmuir model exhibited the best fit to experimental data. According to this isotherm model, the maximum Ni(II) biosorption capacity of LCS is 66.62 mg g(-1). The calculated thermodynamic parameters showed that the biosorption of Ni(II) ions is an endothermic and non-spontaneous process. Results indicate that LCS can be used as an effective and environmentally friendly biosorbent to detoxify Ni(II)-polluted wastewaters.

Corncob as an effective, eco-friendly, and economic biosorbent for removing the azo dye Direct Yellow 27 from aqueous solutions

The corncob is an agricultural waste generated in huge quantities during corn processing. In this paper, we tested the capacity of corncob particles for water purification by removing the azo dye Direct Yellow 27 (DY27) via biosorption. The biosorption process was investigated in terms of the kinetics, equilibria, and thermodynamics. Batch biosorption studies showed that the biosorption performance has strong inverse correlations to the solution pH and the corncob particle size, and it increases quickly with increasing contact time and initial dye concentration. The pseudo-second-order kinetic model provides the best fit to the experimental data, whereas the Redlich-Peterson isotherm model is most suitable for describing the observed equilibrium biosorption. The biosorption process is exothermic, spontaneous, and physisorption in character. Fourier transform infrared (FTIR) spectroscopy and confocal scanning laser microscopy (CSLM) studies suggest that lignocellulose and proteins play key roles in the biosorption of DY27 from aqueous solutions by corncob. Furthermore, after biosorption onto the corncob, the dye can be effectively desorbed using 0.1 M NaOH solution. Therefore, the corncob can be used as a promising biosorbent to remediate DY27-contaminated water and wastewater.

Biodegradation of Methyl Tertiary Butyl Ether (MTBE) by a Microbial Consortium in a Continuous Up-Flow Packed-Bed Biofilm Reactor: Kinetic Study, Metabolite Identification and Toxicity Bioassays

This study investigated the aerobic biodegradation of methyl tertiary-butyl ether (MTBE) by a microbial consortium in a continuous up-flow packed-bed biofilm reactor using tezontle stone particles as a supporting material for the biofilm. Although MTBE is toxic for microbial communities, the microbial consortium used here was able to resist MTBE loading rates up to 128.3 mg L-1 h-1, with removal efficiencies of MTBE and chemical oxygen demand (COD) higher than 90%. A linear relationship was observed between the MTBE loading rate and the MTBE removal rate, as well as between the COD loading rate and the COD removal rate, within the interval of MTBE loading rates from 11.98 to 183.71 mg L-1 h-1. The metabolic intermediate tertiary butyl alcohol (TBA) was not detected in the effluent during all reactor runs, and the intermediate 2-hydroxy butyric acid (2-HIBA) was only detected at MTBE loading rates higher than 128.3 mg L-1 h-1. The results of toxicity bioassays with organisms from two different trophic levels revealed that the toxicity of the influent was significantly reduced after treatment in the packed-bed reactor. The packed-bed reactor system used in this study was highly effective for the continuous biodegradation of MTBE and is therefore a promising alternative for detoxifying MTBE-laden wastewater and groundwater.